Sweden stepped up a military operation off the coast of Stockholm on Saturday following what it described as “foreign underwater activity”.<br /><br />Since Friday evening, ships, helicopters and about 200 troops have been involved in the search of the Baltic Sea following a tip-of from what it said was a trustworthy source.<br /><br />Navy leaders later said they had widened their presence around the Stockholm archipelago, a group of 30,000 islands and islets.<br /><br />The operation has brought back vivid memories of the final years of the Cold War when Sweden repeatedly hunted alleged Soviet submarines along its coasts with depth charges.<br /><br />Swedish defence analysts have speculated that a foreign submarine may have been in the area to replace old spy equipment.<br /><br />The operation comes amid increasing tension with Russia among the Nordic and Baltic states over the Ukraine crisis. <br /><br />Last week, Finland accused the Russian navy of interfering with a Finnish environmental research vessel in international waters.
